After releasing an initial set of basic APIs for Google+, the company is exposing more functions that external developers can access for the tools and applications they build for the social networking site.

Google is also boosting the site's privacy controls for end users, adding a feature that lets people disable others' ability to re-share and comment on one of their posts before publishing it.

The new API (application programming interface) features include access to the site's search engine, so that applications can tap into it and look for public posts and public profile information like members' names, biographical sketch and location.

Also new is the ability for applications to access data on who re-shared a public post and who tagged it with a +1 click, as well as read comments made to public posts. Google released the first batch of Google+ APIs in mid-September.

Google launched the social networking site in late June with high hopes that it can make a run at Facebook, whose dominance of this market has Google nervous.

Not only has Facebook become one of the most popular sites in the world and a major advertising player, it holds a massive amount of content to which Google's search engine has limited access.

Facebook also has a tight partnership with Google rival Microsoft, whose Bing search engine has broader access to Facebook content.

Google+ was initially available only by invitation, but Google opened it up to all comers two weeks ago.

Google is emphasizing the site's privacy features, arguing that it provides a simpler and more effective way for users to control who has access to the content they post.

However, Facebook has unfurled a raft of upgrades to its site since the launch of Google+ in late June, including a revamping of its privacy controls, a video chat feature and a simplified and automated way of segmenting the friends list into different groups.

Facebook also recently started letting members add a "subscribe" button to their profiles, so that non-friends can receive their public posts on their activity stream.

Facebook plans to roll out in the coming weeks a major redesign of member profile pages called Timeline, intended to make it easy for visitors to see not only recent posts but also years-old information.

In addition, an upgrade to Facebook's application development platform now lets gaming and media companies more tightly integrate their content and services with the site.

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